Previous studies indicate that cell-mediated immunity (CMI) plays a significant role in the pathophysiology of periodontal disease. These studies have measured various cell-mediated immune responses of peripheral blood leukocytes to dental plaque antigens. It appears that the distribution of the local gingival leukocyte population is different from that found in peripheral blood. Additionally, the local gingival environment is rich in factors known to modify CMI, namely, antigen, antibody, and antigen-antibody complexes. Therefore, the response of gingival crevice leukocytes to plaque antigens may be significantly diffferent from that mediated by peripheral blood leukocytes. Gingival crevice leukocytes may also be susceptible to serum elements which can modify CMI. The objectives of the proposed study are to compare the immune characteristics and functional relationships of gingival crevice and peripheral blood leukocytes. Comparable populations of leukocytes isolated from the gingival crevice and peripheral blood will be examined for immune surface receptors. The ability of each population to mediate antibody-dependent cell-mediated cytotoxicity will be studied. Using a dual chamber system, the functional relationships between subpopulations of leukocytes will be examined for each cell source. Using salt fractionation, column chromatography, ultrafiltration, affinity chromatography, acrylinde gel electrophoresis, and immunoelectrophoresis, preparation of antigen, antibacterial antibody, and immune complexes will be isolated from human serum and rabbit antibacterial serum. These compounds will be tested for their ability to modify in vitro assays of immune function mediated by both gingival crevice and peripheral blood leukocytes.